The military arm of North Korea’s government released a statement on Friday, declaring that the deployment of American THAAD missile systems in South Korea would be met with “physical action.”

The statement, released through North Korea’s official media outlet, KCNA, went on to accuse the United States of colluding with South Korea in a plot to mount a “preemptive attack on the North,” adding that this development has brought the Korean peninsula to the “brink of a nuclear war,” and suggesting that the North Koreans would consider a nuclear response to the American armament.

Their response came directly after American Secretary of Defense, James Mattis, dismissed China’s complaints about the US deploying THAAD missile systems in both South Korea and Japan. During a public meeting with his South Korean counterpart, Mattis addressed North Korean hostility specifically as the reason for the American anti-missile defense system, or THAAD, to be stationed in South Korea.

“North Korea continues to launch missiles, develop its nuclear weapons program and engage in threatening rhetoric and behavior,” Mattis said.  “Any attack on the United States or on our allies will be defeated and any use of nuclear weapons will be met with a response that will be effective and overwhelming.”

North Korea’s military responded by accusing the United States of misrepresenting what the THAAD missile system is intended for, calling it an “invasion tool” and accusing the United States of pursuing “world supremacy.”

“There will be physical response measures from us as soon as the location and time that the invasionary tool for US world supremacy, THAAD, will be brought into South Korea are confirmed,” the North’s military said in a statement.

“We once again warn the enemies that it is the steadfast will of the KPA [Korean People’s Army] to make merciless retaliatory strikes to reduce South Korea to a sea in flames, debris once an order is issued.”

South Korea’s president defended the placement of the THAAD missile system in his country, calling it a “purely defensive” system.